To get hold of visa by applying it from the Vietnam embassies in India the unit of issue is the embassy itself. Time for processing is 4 to 5 days of working. The application of visa requires your passport to be submitted along. The validity of your passport must be up to six months to apply for visa through embassy. The embassies of Vietnam in India are located in Delhi so you need to go to Delhi if you are not a resident of Delhi. There are consulates in Mumbai as well for Vietnam from where you will get all the information. Note that procedures, regulations and fees are subjected to change.
As far as visa on arrival is concerned, you have to travel air. The application form is available online which you have to fill in or you can download it and then you have to send the form along with a copy of the scanned passport. The fee for service will be provided to you through a link and the other provisions are same. The approval letter for visa will be provided to you after 1 or 2 days of working and then when you arrive at the Vietnam airport your visa will be stamped but you have to make sure that you carry the approval letter and the passport with you. Two passport size photographs are also required.
Visa on arrival is considered to be a convenient method of procuring visa in comparison to getting visa by embassy and is a lot better for all those Indians who do not stay near to the embassy. The unit of issue as far as visa on arrival is concerned is the Immigration Department of Vietnam. Service fees have to be paid online as well but you need to take few dollars all the way in the flight so as to give it at the airport as part of the stamping fee. Visa on arrival is as legitimate as the visa you get it from embassy. It is for all those passengers who cannot stand the lengthening procedure of procuring visa from the embassy.
Without fail you will get the visa on arrival on reaching the airport and there is no hidden charge associated with it. The procedure however for visa on arrival is quite simple in comparison to getting visa from the embassy. Fees for visa on arrival are also cheap when you compare it with visa from embassy.